1. Field of the Invention
This invention relates to novel hydrosilylation catalysts and silicone compositions having the same blended therein.
2. Background Art
From the past, addition reaction between aliphatic unsaturated bonds and hydrosilyl radicals promoted by platinum group metal catalysts is utilized in a variety of applications. Inter alia, platinum compounds which contain platinum atom as a catalytic metal are used as catalytic compounds finding the most versatility in the field. Beside organic synthetic reaction such as synthesis of silalkane bonds, platinum compounds are also utilized in the silicone industry as means for crosslinking addition reaction type resins and rubbers. Applications include use as adhesives, coating agents, potting agents, gelling agents, and foaming agents, and extrusion, compression molding or injection molding of liquid or millable rubbers. In these fields, a fast-curing composition having a long shelf life is demanded from the working and operating standpoints.
For compositions utilizing addition reaction as the crosslinking system, a number of proposals have been made on controlling agents for controlling the shelf life and pot life of platinum catalysts. The controlling agents proposed heretofore include benzotriazole compounds (JP-B 25069/1965 corresponding to U.S. application Ser. No. 202,974 filed Jun. 18, 1962), acetylene alcohol compounds (JP-B 31476/1969 corresponding to U.S. Pat. No. 3,445,420), vinyl-containing polysiloxane compounds (JP-B 10947/1973 corresponding to U.S. Pat. No. 3,699,073), hydroperoxides (JP-B 20340/1982 corresponding to U.S. Pat. No. 4,061,609), and amine compounds (JP-A 56563/1988 corresponding to EP 257,970). However, such chemical control has a limit in finding a compromise between pot life and curing rate, failing to meet the current market demand for prolonged storage and fast curing.
From the above standpoint, an attempt was made to enclose platinum catalysts in thermoplastic resins or silicone resins so that the catalysts may be released to silicone compositions at elevated temperature causing the thermoplastic resins or silicone resins to be melted. This technology is disclosed in many patents, for example, JP-A-134786/1974, JP-A 37053/1983 corresponding to U.S. Pat. No. 4,481,341, JP-A 51140/1989 corresponding to U.S. Pat. No. 4,874,667 and U.S. Pat. No. 5,009,957, JP-A 9448/90 corresponding to U.S. Pat. No. 5,015,716, JP-A 14244/1990 corresponding to U.S. Pat. No. 5,017,654, JP-A 202193/1993 corresponding to EP 543,410, and JP-A 196921/1995 corresponding to EP 661,349.
The encapsulation of platinum catalysts in thermoplastic resins or silicone resins, however, has several drawbacks. There occurs a time lag until the resins are dissolved. Although the thermoplastic resins or silicone resins have a good film-forming capability because of high molecular weight substances, there also occurs a time lag in dissolution temperature unless their molecular weight distribution is controlled. A substantial variation occurs between synthesis lots.
Therefore, an object of the invention is to provide a novel hydrosilylation catalyst for curing of room temperature or heat curing type silicone compositions, which has a long storage life, fast-curing capability, ease of preparation, and consistent quality among lots. Another object is to provide a silicone composition having the hydrosilylation catalyst blended therein, which invites little or no time lag with respect to curing temperature and reaction rate.